Camera with lens disc stopping system

ABSTRACT

A camera including an automatic lens focusing system, wherein a disc holding a plurality of different lens elements is rotated to sequentially present the lens elements at a focusing system, is provided with a disc stopping arrangement comprising a plurality of notches in a peripheral section of the disc and a pawl having a tang therein configured to be received in a selected one of the notches to stop disc rotation and locate a corresponding one of the lens elements at the focusing position. The outer edge portion of the disc, the notches and the pawl tang are specially configured so as to stabilize the pawl prior to tang entry into a notch and to efficiently dissipate inertial energy of the disc.

BACKGROUND OF THE INVENTION

The present invention relates to the field of photography and, moreparticularly, to a camera including an automatic lens focusing system.

Commonly-assigned U.S. Pat. No. 4,167,316 and copending applicationsU.S. Ser. Nos. 017,196, and 017,425, now U.S. Pat. No. 4,243,309, bothfiled on Mar. 5, 1979, and U.S. Ser. No. 156,044, filed on June 3, 1980,disclose cameras of the type including an automatic lens focusing systemthat is formed in party by a sonic ranging system for measuring thephotographic subject-to-camera distance.

Typically, the lens focusing system includes a plurality of discretelens elements, each having a different focal length, mounted incircumferentially spaced apart relation on a lens holding disc forrotation about a disc center axis to sequentially present the lenselements at a focusing position for focusing image forming light raysemanating from a subject located within a correspondingsubject-to-camera distance range at the camera's film plane.

As the sonic ranging system (which may be of the type described incommonly-assigned U.S. Pat. No. 4,199,246) operates, the disc isaccelerated by the arm of a torsion spring or the end of a pivotingactuator member to impart rotary motion thereto. After receipt of anecho signal from the subject indicative of subject distance, a disc pawloperates to engage a corresponding one of a plurality of notches or tabsdisposed about the periphery of the disc to thereby stop disc motion andlocate the lens element corresponding to the indicated distance range atthe focusing position.

Those skilled in the photographic art will appreciate that a lapsed timeperiod from the beinning to the end of the automatic lens focusingportion of the camera cycle is relatively short. Typically, with a lensdisc having four separate lens elements thereon, the lens pawl stops thedisc to locate the first element at the focusing position withinapproximately 25 milliseconds after cycle initiation. The elapsed timefor stopping the last of the four lens elements at the focusing positionis approximately 80 milliseconds.

To insure that such rapid operation is performed reliably on aconsistent basis, it is essential for the lens drive system to quicklyand smoothly accelerate the lens disc to a substantially constantrotational velocity and for the disc or lens pawl to interactdynamically with the disc and the notches therein in a consistent andreliable manner to stop the disc by dissipating its inertial energy insuch a way as to minimize disc oscillation and also to stabilize theposition of the disc at each of its four focusing locations toaccurately align the corresponding one of the lens elements with anexposure opening leading to the film plane.

In the previously-noted U.S. Pat. No. 4,167,316 the disc is providedwith a series of tabs on the peripheral section extending outwardly in adirection transverse to the plane of rotation of the disc and the lenspawl includes a stop thereon which moves into the locus of travel of thetabs on stop disc rotation at the appropriate time. After engagement ofthe stop with one of the tabs, a torsion spring rotates the disc in theopposite direction so that the stop then becomes engaged with the tabassociated with the next adjacent lens to locate it at the focusingposition. The very nature of this action necessarily includes some discbounce and oscillation which may lead to undesirable variation in theactual stopping time of the lens disc in each of its four focusingpositions.

In the previously-noted copending applications, the disc is providedwith notches having a shape that is generally complementary to the shapeof the tang on the lens pawl. Initially, the pawl is in a retractedposition so that the tang is outside of the locus of travel of the discperipheral edge. In response to the echo signal indication, the lenspawl is pivoted toward the disc so that the tang rides along the edge ofthe disc in between adjacent notches until its leading edge engages acorresponding angled camming surface on the notch whereby it is cammeddown into the notch to stop disc rotation. It will be noted that theperipheral edge in between adjacent notches radiates inwardly toward thenotch to promote radially inward movement of the tang in preparation forits receipt into the approaching notch. However, such movement of thelens pawl caused by the changing radius of the peripheral edge may leadto a certain amount of instability in the lens pawl which couldadversely effect the movement of the tang into the notch. Also, thecomplementary camming surfaces along the sides of the notch and tanghave to be critically aligned so as not to bind, therefore making thepiece parts more complex and expensive than is necessary.

Therefore, it is a primary object of the invention to provide a camerawhich includes such an automatic lens focusing position wherein theperipheral section of the disc including the notches and the tang on thelens pawl are configured to facilitate smooth cooperative operation tostop rotation of the lens disc in a more consistent and reliable manner.

Other objects of the invention will, in part, be obvious and will, inpart, appear hereinafter.

SUMMARY OF THE INVENTION

The present invention provides a camera including an automatic lensfocusing system of the general type previously described forautomatically focusing image forming light rays from a photographicsubject at the camera film plane.

The disc holding the plurality of lens elements in circumferentiallyspaced apart relation thereon includes a peripheral section having aplurality of open outer end tang receiving notches therein extendinggenerally inwardly from an outer edge portion of the disc. Each of thenotches is arranged in predetermined angular relation to a correspondingone of the lens elements and is also configured to include a leadingside cam surface set at a cam angle with negative rake; an oppositelyspaced trailing side cam surface set at a cam angle with positive rakeand extending further out in a radial direction than the leading sidecam surface; a bottom surface; and a generally concave energydissipating transition ramp surface extending between a lower portion ofthe trailing side cam surface and the bottom surface. The outer edgeportion is set at a constant radial distance from the axis betweennotches except in the vicinity of the outer ends of the trailing sidecam surfaces where it protrudes outwardly to accommodate the extendedportion of the trailing side cam surfaces.

A lens pawl is responsive to the provision of the echo signal indicationfor stopping rotation of the disc to locate a corresponding one of thelens elements at the focusing position. The pawl is mounted for pivotalmotion toward and away from the peripheral section of the disc andincludes thereon a tang configured to be releasably received in any oneof the disc notches to stop disc rotation and inhibit further rotationuntil it is removed from the notch.

The tang is configured to include a leading side surface having apositive rake angle that is greater than the cam angle of the trailingside cam surface of the notches; a trailing side surface having anegative rake angle that is greater than the cam angle of the leadingside cam surface, and a concave bottom surface. The bottom surface has aradius of curvature that is smaller than the radius of curvature of thedisc outer edge portion between notches and joins the lower ends of thetang leading and trailing side surfaces thereby defining leading andtrailing end tang cam follower tips. The span between the leading andtrailing tips is narrower than the width of the notch opening.

The pawl is initially locatable in a disengaged position where the tangis spaced outwardly from the outer edge portion to allow rotation of thedisc therepast. In response to the echo signal indication, it isactuable to pivot toward the disc so that at least one of the leadingand trailing end tips engages the outer edge portion of the disc betweenadjacent notches ahead of an approaching one of the notches and ridestherealong whereby the lens pawl is maintained in a stabilized conditiondue to the constant radius of the outer edge portion until the leadingend tip of the tang is engaged by the extended portion of the trailingside cam surface of the approaching notch. Thereupon, in response tofurther disc rotation toward the focusing position, the leading end tipfollows the trailing side cam surface and thereafter the concave rampsection to effect camming action of the tang down into the notch toinitiate stopping of disc rotation. The trailing end tip of the tang inthe leading side cam surface of the notch also act to cam the tang intothe notch when engaged in response to oscillating action of the disc dueto abrupt disc deceleration when the tang enters the notch.

The disc further includes means for biasing the disc back towards theinitial position and this counter rotation of the disc serves to holdthe leading side cam surface of the notch in contact with the trailingend tip of the tang located therein to accurately position the disc andthereby locate the corresponding lens element at the focusing position.

It has been found that the provision of the concave ramp section in thenotch substantially aids in the dissipation of the inertial enery of thedisc to facilitate stopping disc rotation with a minimum of oscillation.

Other aspects of the camera disclosed herein are disclosed and claimedin commonly-assigned copending applications U.S. Ser. Nos. 222,011 and222,013 filed on even date herewith.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawings wherein:

FIG. 1 is a block circuit diagram of a camera embodying the presentinvention;

FIG. 2 is a front elevational view showing portions of an automatic lensfocusing system and shutter blade mechanism;

FIG. 3 is similar in some respects to FIG. 2 but shows a shutter latchand lens disc actuator in an unlatching position;

FIG. 3A is a cross-sectional view taken along the line 3A--3A in FIG. 3;

FIG. 4 is a front elevational view showing portions of the automaticlens focusing system and shutter blade mechanism in still anotherposition;

FIG. 5 is an elevational view showing the tang of a lens pawl ridingalong the peripheral edge of a lens disc;

FIG. 6 is an elevational view that is similar in some respects to FIG. 5but shows the tang of the lens pawl located in a receiving notch alongthe periphery of the lens disc;

FIG. 7 is a diagrammatic view of a testing and calibration set up forthe lens focusing and shutter blade mechanism module;

FIG. 8 is an elevational view showing the disposition of an arcuate armon the lens pawl in relation to a light transmission slit when the tangof the lens pawl is riding along the peripheral edge of the disc; and

FIG. 9 is similar in some respects to FIG. 8 but shows the dispositionof the arcuate arm on the lens pawl when the tang thereof is received ina notch formed in the peripehry of the lens disc.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1, a photographic camera apparatus 10 embodying the presentinvention is shown in simplified block diagram form. The cameraapparatus 10 includes an objective lens arrangement or assembly, asshown in simplified fashion at 12, disposed for movement between aplurality of different focal positions which correspond respectively todifferent camera-to-subject distance ranges. During each film exposureoperation, the objective lens assembly 12 is displaced to one of itsfocal positions for focusing, at a film plane 14, image forming lightrays from a photographic subject, as suggested at 16, located within oneof the distance ranges from the camera. As is readily apparent, the lensassembly 12 is adapted, at each of its plurality of focal positions, tofocus at the film plane 14 an image of a photographic subject located ata different distance from the camera within the corresponding distancerange. The lens assembly 12 is preferably driven through its pluralityof different focal positions in a manner to be described in greaterdetail herein and may be releasably held at any one of its differentfocal positions by lens stopping means including a releasable lens pawl20 which also will be described in greater detail later.

When lens assembly 12 is at its initial terminal position, it operatesto focus image forming light rays from a photographic subject located atthe closest possible distance range to the camera within theaforementioned camera-to-subject distance ranges and when in its otherterminal position (phantom lines) operates to focus image forming lightrays from a photographic subject located at the furthest possibledistance range from the camera within the aforementionedcamera-to-subject distance ranges. The movement of the lens assembly 12from its initial terminal position toward its other terminal positionsoperates to progressively focus image forming rays for correspondingsubjects located at progressively increasing distance ranges from thecamera.

Camera 10 is also provided with a sonic rangefinder as shown generallyat 22 and which is more fully described in U.S. Pat. No. 4,199,246entitled "Ultrasonic Ranging System For A Camera" by J. Muggli, issuedApr. 22, 1980, and U.S. Pat. No. 4,167,316 entitled "Sonar ControlledLens Focus Apparatus" by B. Johnson et al., issued Sept. 11, 1979 incommon assignment herewith and now incorporated by reference herein.

The sonic rangefinder 22 includes a range signal transmitting circuit 24which is actuated in a manner to be described later to issue a transmitcommence signal to a sonic transducer 28 so as to cause therefrom thetransmission of a sonar ranging signal comprising a burst of sonicenergy as suggested at 30. Thereafter, the transducer 28 operates todetect an echo signal reflected from the photographic subject 16. Anecho detector circuit 32 connected to transducer 28 then provides asignal indicative of the elapsed time between the transmission of thesonar ranging signal and the detection of the echo signal whichcorresponds directly to the distance between the camera and the subject16. The manner in which the ranging information provided by rangefinder22 is utilized in camera 10 will become apparent later on in thedisclosure.

Between the objective lens arrangement 12 and the film plane 14 there isprovided a shutter mechanism that is shown generally at 34 comprisingtwo overlapping shutter blade elements 36 and 38 (see FIGS. 2-4) of theso-called scanning type which will be described in greater detail laterherein. Camera 10 is also provided with a photographic cycle initiatingbutton, shown at 40 in FIG. 1, which is manually actuable to commence anexposure interval by ultimately affecting the release of the shutterblade elements 36 and 38 in a manner to be described later.

Referring now to FIGS. 2-4, it will be seen that a pair of scene lightadmitting primary apertures 44 and 46 are provided respectively in theblade elements 36 and 38 to cooperatively define a progressive variationof effective aperture openings in accordance with simultaneouslongitudinal and lateral displacement of one blade element with respectto the other blade element in a manner fully described in U.S. Pat. No.3,942,183 entitled "Camera With Pivoting Blades" By G. Whiteside, issuedMar. 2, 1976 and assigned in common herewith. The apertures 44 and 46are selectively shaped so as to overlap a light entering exposureopening 48 in a base block structure 49 mounting various components,thereby defining a gradually varying effective aperture size as afunction of the position of the blade elements 36 and 38.

Each of the blades 36 and 38 may additionally configured to havecorresponding photocell sweep secondary apertures shown respectively at50 and 52. Secondary apertures 50 and 52 may be configured incorrespondence with the shapes of the scene light admitting primaryapertures 44 and 46. As is readily apparent, the secondary apertures 50and 52 also move in correspondence with the primary apertures 44 and 46to define a small secondary aperture for admitting the passage of scenelight to a light detecting or photoresponsive element 54 mounted in thebase block 49 as best seen in FIG. 4.

Projecting outwardly from the base block 49 at a location spaced to theright side of the exposure opening 48 is a pivot pin or stud 56 whichpivotally and translatably engages elongated slots 58 and 60 formed,respectively, in the shutter blade elements 36 and 38. Pin 56 may beintegrally formed with the base block 49 and the blade elements 36 and38 may be retained in engaging relation with respect to the pin 56 byany suitable means such as peening over the outside end of pin 56.

The opposite ends of the blade elements 36 and 38 include extendedportions which pivotally connect to a walking beam 62. The walking beam62, in turn, is disposed for rotation relative to the base block 49 by apivotal connection to a projecting pivot pin or stud 64 which may beintegrally formed with the base block 49 at a location to the left ofexposure opening 48. The walking beam 62 may be pivotally retained withrespect to the pin 64 by any conventional means such as the illustratedsnap ring 65.

In a preferred embodiment, the walking beam 62 is pivotally connected atits distal ends to the shutter blade elements 36 and 38 by respectivepin members 66 and 68 which extend inwardly from the walking beam towardbase block 49. Pin members 66 and 68 are preferably circular incross-section and extend through respective openings in blade elements36 and 38 so as to slidably engage corresponding arcuate tracks orchannels 70 and 72 which may be integrally formed in the base block 49.The arcuate channels 70 and 72 operate to inhibit disengagement of theblade elements 36 and 38 from their respective pin members 66 and 68during operation of the exposure control system. Thus, the walking beam62 and the shutter blade elements 36 and 38 collectively define a blademechanism together with a means for mounting the blade mechanism fordisplacement including the pivot pins 56 and 64.

Drive means are provided for displacing the blade mechanism 34 andinclude an opening tension spring 73 and a tractive electromagneticdevice such as a solenoid, shown generally at 74, for rotating walkingbeam 62 to displace the shutter blade elements 36 and 38 with respect toeach other and the base block 49 in a manner to be subsequentlydescribed herein. The tension spring 73 is connected at one end to ananchor member 75 which may be secured to structure on an outside coverplate 77 oppositely spaced in front of base block 49; and at its otherend to an outwardly extending post 79 on walking beam 62 so as toyieldably bias the walking beam 62 to rotate in a clockwise directionabout pivot pin 64.

The solenoid 74 includes an internally disposed cylindrical plunger unit76 which retracts inwardly into the body of the solenoid uponenergization of the solenoid winding. The solenoid plunger 76 includesan end cap 78 at the outside end thereof together with a vertical slotor groove 80 within the end cap 78 for loosely engaging a pin 82extending outwardly from post 79. In this manner, the solenoid plunger76 is attached to the walking beam 62 so that longitudinal displacementof the plunger 76 operates to rotate the walking beam around the pivotpin 64 and thereby displace the shutter blade elements 36 and 38.

The walking beam 62 also controls operation of the lens pawl 20 andtherefore additionally includes an integrally formed pawl actuator armportion 84 extending outwardly therefrom to define an integral taperedoutside end section 86 having a rounded tip. The end section 86 isconfigured to be received in a generally conforming notch portion 88 onthe lens pawl 20 for reasons which will become more apparent later.

In order to maintain the shutter blade elements 36 and 38 in their scenelight blocking arrangement, wherein apertures 44 and 46 do not overlapat all, such as in FIGS. 2 and 3, without requiring the continuousenergization of the solenoid 74, there is provided a combined walkingbeam latch and lens actuator member 90 disposed for rotation about apivot pin or shaft 92 which may be integrally formed with the base block49. At its upper left-hand end, the latch and actuator member 90includes an inwardly projecting integrally molded latch tang 94 which isoperative when member 90 is in its latching position of FIG. 2 to extendinto the locus of travel of the walking beam 62 to engage a notch ordetent 96 thereon for inhibiting clockwise rotation of the walking beam62 by the tension spring 73. Spaced below the latch tang 94, the latchand actuator member 90 further includes a longitudinally extending arm98 engaged by the end of an actuator arm 100 which generally defines ayoke having one side portion thereof formed by an integral spring finger102 as best shown in FIG. 3A. The actuator arm 100 is moved downwardlyand then upwardly in a manner more fully described in U.S. Pat. No.4,040,072 entitled "Shutter Latch Arrangement Releasable Through ShutterBlade Actuation And Resettable Through Film Advancement" by B. Johnsonet al., issued Aug. 2, 1977, and operates to first impartcounterclockwise rotation to the latch and actuator member 90 in amanner as will be more fully described herein.

In a preferred embodiment, the aforementioned objective lens arrangement12 comprises a plurality of different lens elements 104a-104d mounted ona disc-like lens holding member 106 disposed for rotation about a centerpivot pin or axis 108 which may be integrally formed and projectoutwardly from the base block 49. In a preferred illustrated embodiment,disc 106 is a unitary piece part molded from clear optical qualityplastic with the lens elements 104a-104d integrally molded therein incircumferentially spaced apart relation and also including an integrallyformed center hub 110 that is configured to receive the pivot pin 108.

Each of the lens elements 104a-104d has a different focal length anddepth-of-field characteristic and corresponds respectively to adifferent one of the aforementioned plurality of focal positions as ismore fully described in U.S. Pat. No. 4,192,587 entitled "ProportionalFill Flash" by A. LaRocque et al. issued Mar. 11, 1980 in commonassignment herewith and now incorporated by reference herein. Typicalcamera-to-subject distances for the lens elements 104a-104d may beapproximately 2.6 feet, 3.8 feet, 9 feet and 24 feet, respectively.

As is now readily apparent, rotation of the lens holding disc 106 aboutthe pivot pin 108 from its initial position shown in FIGS. 2 and 3operates to sequentially move each of the lens elements 104a-104d intoposition overlying the exposure opening 48 in the base block 49 so as tosequentially focus images onto the film plane 14 of the camera ofphotographic subjects located at progressively increasing distanceranges from the camera.

Those skilled in the art will understand that additional lens elements(not shown) may be provided in fixed optical alignment with the exposureopening 48 and cooperate with lens elements 104a-104d to define theobjective lens arrangement 12 for the camera 10. Thus, one of the lenselements 104a-104d may be entirely omitted, with an open space providedin its place whereupon the additional lens elements provided in opticalalignment with exposure opening 48 to define the camera objective lenswhen the open space is rotated into position over the exposure opening48. The lens elements 104a-104d preferably would be relatively weak incomparison with other lens elements (not shown) in optical alignmenttherewith.

The lens holding disc 106 is spring biased for counterclockwise rotationabout pin 108 toward its initial position of FIG. 2, where an outwardlyextending integrally formed acceleration tab 112 on the outer peripheralsection of disc 106 engages a fixed stop pin 114 mounted on the coversection 77, by a first torsion spring 116. Torsion spring 116 has itscenter portion coiled about hub 110 and includes a first relatively longspring arm 118 having its end fixedly secured to a tab 120 on base block49, and a shorter arm 122 captured in an integrally molded detent 124 ondisc 104 adjacent hub 110.

Means for effecting clockwise rotation of lens disc 106 about pivot pin108 against the bias of torsion spring 116 to sequentially present eachof the lens elements in registration with exposure opening 48 isprovided in the form of a second torsion spring 126. Torsion spring 126also has its coiled center portion mounted on hub 110 on top of thecoiled portion of torsion spring 116 and includes a fixed arm 128 havingits end captured in a selected one of an arcuate array of detents onmember 130 formed on the cover plate 77, and its opposite accelerationarm 132 radiating outwardly from hub 110 to locate its distal end 134 inthe locus of travel of the upstanding tab 112 on the periphery of disc106.

As best shown in FIG. 2, the latch and actuator member 90 also serves toreleasably hold acceleration arm 132 in a cocked initial positionwherein the end 134 of acceleration arm 132 is spaced behind tab 112. Itshould be noted that stop 114 engages an upper end of tab 112 and thatthere is sufficient clearance thereunder for the end 134 of accelerationarm 132 to slide under stop 114 and engage tab 112 upon release of arm132 to impart clockwise rotation to disc 106.

To releasably hold acceleration arm 132 in the initial cocked position,the latch and actuator member 90 includes an elongated portion extendingto the right of pivot pin 92 and having a generally triangular uppersection 136 that terminates in an upstanding outwardly extending tabportion 138 for engaging a mid portion of acceleration arm 132.

As will become apparent later, in response to the rapid pivotal motionof member 90 in a counterclockwise direction about pivot pin 92 to theshutter unlatching position shown in FIGS. 3 and 4, the end portion 136of member 90 having tab 138 thereon moves upwardly to thereby releaseacceleration arm 132 which pivots in a clockwise direction to strike tab112 to effect clockwise rotation of disc 106. In response to clockwiserotation of member 90 back to its shutter latching position, tab 138reengages acceleration arm 132 and moves it back therewith to its energystoring initial position of FIG. 2. Thus, in addition to its function ofreleasably latching the shutter blade mechanism 34 through its operativeassociation with walking beam 62, member 90 also serves to releasablyhold the acceleration arm 132 of torsion spring 126 in its initialenergy storing cocked position; to release arm 132 for engagement withtab 112 to effect disc rotation in a clockwise manner; and thereafter torecock the disk drive means or torsion spring 126 by moving accelerationarm 132 from its second terminal position back to its initial position.

The clockwise rotation of disc 106 is stopped selectively by theoperation of lens pawl 20 which includes a tang portion 140 thereon thatis configured to be received in any one of four notches 142a-142ddisposed about the periphery of disc 106 in circumferentially spacedapart relation for locating a corresponding one of the lens elements104a-104d respectively in registration with the exposure opening 48. Theconfiguration of notches 142a-142d will be described in detail later on.

The lens pawl 20 includes a pivot arm 144 which terminates at one end intang 140 and has at its other end an integrally formed hub section 146which is adapted to receive a pivot pin 148 integrally formed andextending outwardly from the base block 49. Integrally formed on theoutwardly facing surface of arm 144 adjacent tang 140 is thepreviously-noted, generally conforming notch or detent 88 for receivingthe tapered end portion 86 of the pawl actuator arm 84 on walking beam62. Pawl 20 is spring biased for counterclockwise rotation about pivotpin 148 by a torsion spring 150 having its coiled center portion wrappedabout hub 146 and including a first spring arm 152 having its endcaptured in a tab detent 154 on base block 49 and a second spring arm156 having its end portion in engagement with a tab 158 on arm 144.Extending outwardly from arm 144 on the side opposite tang 140, is agenerally arcuate shaped arm 160 which will serve a useful purpose in acalibration test for adjusting the speed of rotation of disc 106 as willbe described later on.

With walking beam 62 held by latch and actuator member 90 in its latchedposition of FIG. 2, the pawl actuator arm 84 releasably holds the lenspawl 20 in a retracted initial position against the bias of torsionspring 150 wherein the tang 140 is spaced from the peripheral section ofdisc 106 allowing free rotation of the disc 106 about pivot pin 108. Aswill become apparent later, in response to clockwise rotation of walkingbeam 62, the corresponding pivotal motion of actuator arm 84 will allowpawl 20 to pivot in a counterclockwise direction under the bias ofspring 150 to engage the peripheral edge of disc 106 and then becomeoperatively seated in an appropriate one of the notches 142a-142d tostop rotation of disc 106.

The camera 10 embodying the present invention may also be provided withan integral electronic flash or strobe system (not shown). The strobecharging and triggering circuitry may be of the type well known in theart as is more fully disclosed in U.S. Pat. No. 4,064,519 entitled"Regulated Strobe For Camera With Sixth Flash Inhibit" issued Dec. 20,1977 in common assignment herewith. The strobe system preferably derivescharging power from a flat battery that is insertable within the camerain correspondence with the film pack or cassette in a manner that iswell known in the art relating to Polaroid SX-70 type film cassettes andcameras.

This flat battery in the film cassette is also preferably utilized topower the circuitry in FIG. 1 in its entirety by the way of threeswitches, S1, S2 and S3 in a manner more fully described in thepreviously-noted U.S. Pat. No. 4,040,072. Camera 10 is also providedwith a motor and solenoid control circuit 162 which operates in a manneralso more fully described in the last mentioned patent.

As is readily apparent, the motor and solenoid control circuit 162operates to control the energizing current delivered to the solenoid 74and to an electrical motor 164. The film units intended for use withcamera 10 are preferably of the self-developing type and the motor 164is provided to effect the advancement and processing of theself-developing film units in a well-known manner.

The sonar ranging signal 30 is derived from a clock circuit 166 which ispowered upon closure of the switches S1 and S2 in a manner to besubsequently described herein. The clock pulse from circuit 166 isdirected to a transmit control circuit 168 which controls thetransmission of the clock pulse to the sonic rangefinder 22 as afunction of a logic signal derived upon closure of the switch S3. Theoutput clock pulse from the transmit control circuit 168 is alsodirected to a frequency divide circuit 170 which operates to reduce thefrequency of the clock pulse and thereafter direct the reduced frequencyclock pulse to the input of a multistage binary counter 172. The outputfrom counter 172 is thereafter utilized to sequence an inverter latchnetwork 174 comprising a plurality of inverter latch circuits.Additionally, inverter latch network 174 receives the output from echodetector circuit 32. The output from inverter latch network 174 is fedto the motor and solenoid control circuit 162.

To initiate a photographic exposure cycle, the operator manuallyactuates button 40 so as to close switch S1 in a manner more fullydescribed in the previously-noted U.S. Pat. No. 4,040,072. The closureof switch S1, in turn, operates to energize the motor and solenoidcontrol circuit 162 which, in turn, energizes the solenoid 74 to retractthe plunger 76 inwardly and rotate the walking beam 62 in acounterclockwise direction from its normal at rest position shown inFIG. 2 to the position shown in FIG. 3. During this counterclockwiserotation, the pawl actuator arm 74 effects clockwise rotation of thelens pawl 20 about pivot pin 148 from its position shown in FIG. 2 toits position shown in FIG. 3.

Referring now to FIG. 3, it can also be seen that the aforementionedclockwise rotation of the walking beam 62 operates to displace detent 96out of engagement with the latch tang 94 on latch and actuator member90. Member 90 is thereafter rotated in a counterclockwise directionabout its pivot pin 92 by the downward movement of the actuator arm 100which results directly from the previously-noted manual actuation of thebutton 40 in a manner more fully described in previously-noted U.S. Pat.No. 4,040,072. In this manner, the latch and actuator member 90 isrotated from its latching position of FIG. 2 to its unlatching positionof FIG. 3, thereby allowing the subsequent rotation of the walking beammember 62 in a clockwise direction toward its maximum aperture definingposition upon the de-energization of solenoid 74. Movement of theactuator arm 100 in the downward direction to effect release of member90 also operates to sequentially effect the closing of the switches S2and S3 in a manner that is again more fully described in U.S. Pat. No.4,040,072.

This counterclockwise rotation of member 90 also moves portion 136 andthe acceleration arm holding tab 138 thereon upwardly to thereby releaseacceleration arm 132 for rotation in a clockwise direction. As shown inFIG. 3, the end 134 of acceleration arm 132 has moved forwardly toengage tab 112 and impart clockwise rotation to the disc 106. Once theend 134 of acceleration arm 132 engages tab 112 its further clockwiserotation is slowed down somewhat by the inertia of the disc systemallowing section 136 of member 90 to moved forward at a more rapid rateto the position shown in FIG. 3 thereby providing sufficient clearancefor further clockwise rotation of acceleration arm 132 to acceleratedisc 106 to its operational velocity. As best shown in FIGS. 3 and 4, anenergy absorbing stop, such as the resiliently deformable cylinder 175,may be provided on cover plate section 77 in position to be engaged bythe upper tip of tab section 138 to preclude bouncing of member 90occassioned by its rapid deceleration at the unlatching position.

As best shown in FIG. 4, acceleration arm 132 continues to drive thelens disc 106 by its engagement with tab 112 until the end 134 ofacceleration arm 132 is stopped by a stop pin 177 on the interior ofcover section 77 in the locus of travel of the end 134 of accelerationarm 132.

Movement of the acceleration arm from its initial cocked position ofFIG. 2 to its terminal position of FIG. 4 effects acceleration of thedisc 106 to a substantially constant rotational velocity forsequentially presenting each of the lens elements 104a-104d at theexposure opening 48.

Closure of the switch S3, in turn, operates to power down the solenoid74 from the initial high current energization condition required toretract the plunger 76 to a low current energization condition requiredto hold the plunger in its retracted position as shown in FIG. 3 in amanner more fully described in the previously-noted U.S. Pat. No.4,192,587. The closing of switch S3 also operates to actuate the sonarrangefinder 22 to transmit the sonar ranging signal 30 by providing therequisite logic signal to the transmit control circuit 168 so as totransmit the clock pulse from the clock circuit 166 to the range signaltransmitting circuit 24. The transmit control circuit 168 also directsthe clock pulse to the frequency divide circuit 170 so as to trigger thecounter 172 in correspondence with the transmission of the sonarrangefinding signal 30.

As is more fully described in copending, commonly-assigned U.S. patentapplication Ser. No. 156,044 filed on June 3, 1980 by J. Bagdis et al.and entitled "Autofocus Camera With Electronic Lens Disc Pawl ReleaseArrangement", the counter 172 which was triggered upon transmission ofthe sonar ranging signal 30 sequentially provides a series ofpredetermined timed outputs to inverter latch network 174 correlatingthe position of each of the lens elements 104a-104d with respect to theexposures opening 48 as the disc rotates. Upon detection of the echosignal, circuit 34 also provides an indication to network 174 which isindicative of camera-to-subject distance. The inverter latching networkacts as a logic subsystem in response to these inputs and insures thatits output to circuit 162 for de-energizing solenoid 74 and therebycausing clockwise rotation of the walking beam 62 which will result inthe release of the lens pawl 20, to occur only at such times as willallow the lens pawl tang 140 to engage the periphery of disc 106 in thespace between adjacent notches. This is to make sure that the tang 140does not first engage the disc at the edge of one of the notches 142which may cause the pawl 20 to bounce inadvertently and miss beingreceived in the appropriate notch 142.

Thus, upon provision of the output from network 174 the solenoid 74 isde-energized causing the tension spring 73 to pivot walking beam member62 in a clockwise direction about pivot pin 64 thereby releasing thelens pawl 20 for movement to locate tang 140 between a pair of notches142a-142d. The timing is such that tang 140 will engage the peripheraledge ahead of the approaching notch 142 that is appropriate for locatingthe lens, corresponding to the subject range indicated by the echodetector circuit output at the focusing position in registration withexposure opening 48. A more detailed description of the configuration ofthe notches 142 and the interaction of lens pawl 20 will appear laterherein.

As best shown in FIG. 4, the tang 140 of lens pawl 20 has been receivedin notch 142a to locate lens element 104a in registration with exposureopening 36.

As the proper lens element 104 is stopped at the focusing position,walking beam 62 continues to rotate in the clockwise direction. Suchrotation effects movement of the blade elements 36 and 38 causing theirrespective primary apertures 44 and 46, which up until this point havebeen out of overlapping relation thereby blocking exposure opening 48,to progressively overlap and define an exposure aperture which increasesin size in response to further progressive displacement of the blademembers. Such blade movement also causes the secondary apertures 52 and54 to overlap and unblock the photocell 54 which is monitoring scenelighting conditions. Photocell 54 forms part of a light integratingnetwork (not shown) which provides a trigger signal to circuit 162, whena sufficient quantity of light has been transmitted through opening 48to properly expose the film unit causing the reenergizing of solenoid 74to retract plunger 76 in thereby pivot walking beam 62 in acounterclockwise direction from the position of FIG. 4 to the positionof FIG. 3 to move blade elements 36 and 38 to the exposure terminatingclosed position.

Such rotation of walking beam 62 causes the pawl actuator arm 84 thereonto pivot lens pawl 20 in a clockwise direction to withdraw tang 140 fromnotch 142a and thereby free the disc 106 for counterclockwise rotationback to its initial position under the influence of torsion spring 116.

As this is happening, circuit 162 also energizes motor 164 and itoperates various components in the camera including the film advancingand processing mechanisms and elements of a gear train which effect themovement of actuator arm 100 upwardly to pivot the shutter latch andlens actuator member 90 in a clockwise direction about pivot 92 from theunlatching position shown in FIGS. 3 and 4 back to the latching positionshown in FIG. 2. In response to such movement, the tab 138 on section136 re-engages the acceleration arm 132 and moves it in acounterclockwise direction back to the initial cocked position. Near theend of the motor energization cycle, mechanical elements within thecamera are moved into position for opening switches S2 and S3 to therebyde-energize the system. Upon de-energization of solenoid 74, the walkingbeam 62 pivots in a clockwise direction a short distance, to theposition of FIG. 2, under the influence of tension spring 73 to onceagain re-engage the latching detent 96 thereon with the latch tang 94 onmember 90.

Those skilled in the photographic art will appreciate that the elapsedtime period from the beginning to the end of the automatic lens focusingportion of the camera cycle is relatively short. For example, as morefully described in the previously-noted copending application U.S. Ser.No. 156,044, the disc 106 is stopped by the lens pawl 20 to locate thefirst lens element 104a at the focusing position within approximately 25milliseconds after cycle initiation. The elapse time for stopping thelast lens element 104d at the focusing position is approximately 80milliseconds.

To insure that such rapid operation is performed reliably on aconsistant basis, it is essential for the lens drive system, in the formof torsion spring 116, to quickly and smoothly accelerate the lens disc106 to a substantially constant rotational velocity and for the lenspawl 20 to interact dynamically with the lens disc 106 and the notches142a-142d therein in a consistent and reliable manner to stop the disc106 by dissipating its inertial energy in such a way to minimize discoscillation and also to stabilize the position of the disc 106 at eachof its four focusing locations to accurately align the corresponding oneof the lens elements 104a-104d with the exposure opening 48.

First, we will look at the dynamic interaction of the lens pawl 20 withdisc 106.

As best shown in FIGS. 2-4, the outer peripheral edge 176 of disc 106 isat a constant radial distance from pivot pin 108 except for furtheroutwardly radiating tabs 178 located at the trailing end portion of eachof the notches 142a-142d; and an elongated outwardly projecting portion180 mounting the acceleration tab 112. The reason for portion 180 is tomount the acceleration tab 112 as far outboard from pivot 108 as ispossible without interfering with other components to thereby maximizethe torque arm.

With reference to FIG. 5, it will be seen that each of the notches142a-142d includes a short angled leading edge or side cam surface 182;an oppositely-spaced longer angled trailing edge or side cam surface 184which is formed in part by the front edge of the corresponding tab 178to extend outwardly in a radial direction beyond the peripheral edge176; and a bottom surface 186 which is spaced oppositely the notch entryopening 188 between the upper ends of cam surfaces 182 and 184. Thetransition zone between the lower end of cam surface 184 and bottomsurface 186 is formed as a curved ramp section or radius 190. The curvedtransition zone 192 between the bottom of cam surface 182 and bottomsurface 186 has a smaller radius than ramp section 190.

The longer trailing side cam surface 184 has a positive rake or camangle with respect to the direction of rotation of disc 106 (clockwise)to sequentially present the lens elements at the exposure opening 48,while the shorter leading side cam surface 182 has a negative rake orcam angle. For the purposes of this disclosure, positive rake means thatthe cam angle, C, between the perpendicular or radial line passingthrough the outermost tip of surface 184 and an outwardly directedextension of surface 184 is positive (i.e., in the same direction as theclockwise rotation arrow). Conversely, the cam angle, C, for surface 182is negative with respect to the perpendicular and oppositely directedwith respect to the clockwise rotation arrow. Cam surface 184 is set ata larger cam angle, C, than cam surface 182.

It may be helpful at this point to specify some of the dimensions tomore clearly visualize the construction of a typical disc 106. Thefollowing dimensions are given in inches. The radial distance toperipheral edge is 0.670. The radial distance to the outermost tip oftab 178 is 0.700 so that the extension of surface 184 beyond edge 176 is0.030. The radial distance to the bottom surface 186 of notch 142 is0.605. The notch entry opening 188 is 0.148 as measured between theoutside ends of surfaces 182 and 184. The angular relations are asfollows. Cam surface 184 is set at a cam angle of 20°. The shorter camsurface 182 is set at a cam angle of 5°. The radius, in inches, oftransition ramp 190 is 0.030; and for ramp 192, 0.015. These dimensionsare to be considered approximate and are provided to show the geometricrelationships of the various identified surfaces and therefore are notto be considered a limitation on the scope of the invention hereininvolved.

As will become apparent later, the cam surfaces 184 and 182 serve to camthe tang 140 of lens pawl 20 into notch 142 and their respective camangles are set to provide appropriate camming action at the point wherethey intersect with intersecting lines of action drawn from the pivotcenter 108 of disc 106 and the pivot center 148 of lens pawl 20.

The tank 140 on lens pawl 20 includes a leading edge or surface 194 thathas a positive rake angle, R, that is greater than the cam angle, C, fornotch cam surface 184; and oppositely spaced trailing edge or surface196 set at a negative rake angle that is greater than the cam angle, C,for notch cam surface 182; and a concave bottom edge or surface 198joining the lower end of surfaces 194 and 196 at leading and trailingend tips, 200 and 202 respectively. It will be noted that bottom surface198 is formed to have a smaller radius of curvature than the outerperipheral surface 176 so that when the lens pawl 20 is released by arm84 on the walking beam 62 and is rotated in a counterclockwise directionabout pivot 148 by torsion spring 150 the engagement of tang 140 withedge 176 is at the leading and trailing tips 200 and 202.

The span of bottom surface 198, as measured between tips 200 and 202, is0.146 inches which is slightly narrower than the notch opening 188(0.148 inches). The radius of curvature of surface 198 is 0.400. Therake angle for surface 194 is 25° and for surface 196 is 11°.

As noted earlier, the release of the lens pawl 20 for movement towarddisc 106 is electronically controlled and correlated to the speed ofdisc rotation so that the tang 140 initially engages the disc in thespace between adjacent notches defined by peripheral edge 176 whereby itrides therealong until its leading tip 200 engages the portion of camsurface 184 that extends outwardly beyond edge 176 and tang 140 iscammed downwardly into the notch 142.

In preparation for driving tang 140 into notch 142, it is highlydesirable that the lens pawl 20 be in a stabilized condition as tang 140rides along surface 176. For this reason, it is preferable to configuresurfaces 176 so that it has a constant radius. That is, the tips, 200and 202, are held in engagement with surface 176 due to the biasinginfluence of torsion spring 150 and because there is no variation inradius as tang 140 rides along surface 176 there will be no pivotalmotion of lens pawl 20.

In response to further clockwise rotation of disc 106 from the positionof FIG. 5 to the position of FIG. 6, the lens pawl 20 remains in thisstabilized condition in that the trailing end tip 202 will remain incontact with surface 176 until a point in time just before theapproaching outer end of cam surface 184 engages the leading end tip200.

Upon engagement of surface 184 with tip 200 on tang 140 and in responseto continued rotation of disc 106 in the clockwise direction along withthe biasing force provided on lens pawl 20 by torsion spring 150, tang140 is urged downwardly into the slot as the tip 200 follows theinclined camming surface 184. This camming action dissipates part of therotational energy of the disc. As tang 140 is cammed further down intonotch 142 tips 200 rides along the radius section 190 which, asdetermined by high speed movies, tends to provide a substantial energydissipation function to promote stopping of the disc with a minimum ofoscillation. In some instances, it has been observed that engagement oftip 200 with the radius section 190 causes slight rotation of the disc106 in the opposite (counterclockwise) direction. If the impact ofsurface 184 on tip 200 does cause some rebound or a slight rotation ofdisc 106 in the opposite direction, then the trailing end tip 202 willengage and follow the cam surface 182 which also will provide a downwardcamming action on tang 140 in response to such counterclockwiserotation. The camming angle of surface 182 is shallower than that ofsurface 184 because it operates when the tang 140 is further down intothe notch 142 and is at a different geometric relation with the pivotpoints of the disc 106 and the lens pawl 20. It will be noted that thesteeper rake angles of tang surfaces 194 and 196 provide sufficientclearance with respect to cam surfaces 184 and 182 to insure that thecam following action of the tang is restricted to tips 200 and 202 forbetter control and more reliable operation.

When the disc 106 is stopped, cam surface 182 is urged into engagementwith the trailing end tip 202 of tang 140 due to the gentlecounterclockwise bias on disc 106 provided by the torsion spring 116.Thus, the trailing end tip 202 serves as a precisely located stopagainst which surface 182 bears to accurately locate the correspondinglens disc in registration with the exposure opening 48.

At the end of the exposure cycle, when walking beam 62 is pivoted in acounterclockwise direction to effect clockwise rotation of lens pawl 20to its retracted position, tip 202 rides upwardly along cam surface 182and imparts a slight amount of clockwise rotation to disc 106 againstthe bias of torsion spring 116 to facilitate withdrawal of tang 140 fromnotch 142. Once tang 140 is clear of notch 142, the torsion spring 116provides the energy to effect rotation of disc 106 in a counterclockwisedirection back to its initial position of FIG. 2 where the upper end ofacceleration tab 112 comes into engagement with stop pin 114.

The velocity at which lens disc 106 rotates in a clockwise direction tosequentially present each of the lens elements 104a-104d at the exposureopening 48 is a function of the inertial mass of disc 106, the frictionof the disc pivot, the clockwise torque applied by disc drive spring 126through its acceleration arm 132 and the smaller oppositely directedtorque applied by the disc return spring 116 through its short springarm 122.

Obviously, for the lens focusing system to operate properly, therotational velocity of disc 106 must be set accurately to fall within anallowable range. In the interests of manufacturing and calibrationeconomy, it is highly desirable to provide a simple and accurate methodfor measuring disc velocity and easily manipulated structure foradjusting disc velocity if it is found to be out of the desiredallowable range.

In a preferred embodiment, the lens focusing system is configured toeasily adjust the clockwise torque applied to the disc 106 by the drivespring 126 for controlling disc velocity in the clockwise direction.

The clockwise torque applied to disc 106 is the product of the torsionarm (radial distance between the disc pivot 108 and the acceleration tab112) and the force applied to tab 112 during the angular displacement ofacceleration arm 132 from its cocked position of FIG. 2 to its terminalposition of FIG. 4. The drive force imparted by acceleration arm 132 is,in turn, measured by the difference in the energy stored in spring 126at its cocked position of FIG. 2 and the lower amount of energy storedin spring 128 at the terminal position of FIG. 4 resulting fromdissipation by the angular displacement of acceleration arm 132 awayfrom the fixed arm 128. Because the angular displacement of accelerationarm 132 is constrained within a fixed angular range by tab 138 on member90 at the cocked position and by stop 177, changes in the drive forcemay be most readily made by changing the amount of energy stored inspring 150 located at its initial cocked position of FIG. 2.

The energy stored in spring 126 at the cocked position is proportionalto the displacement angle, d, between the acceleration arm 132 and afixed arm 128. Since acceleration arm 132 is held at a fixed positiondetermined by the location of tab 138 on latch and actuator member 90located in its shutter latching and spring cocking position of FIG. 2,the displacement angle, d, may be adjusted to vary stored energy bychanging the angular disposition of the fixed arm 128.

As noted earlier, the end of spring arm 128 is configured to be capturedin any one of a plurality of detents or notches 204 disposed in anarcuate array on a comb-like detent member 130 formed on the fixed coverplate 77 in front of the lens disc and shutter assembly opposite baseblock 49. The fixed arm 128 is supported in engaging relation with thedetent member 130 by a small bridge member 206 located on cover plate 77between pivot 108 and the interior edge of detent member 130. An opening208 in cover plate 77 between bridge 206 and detent member 130 providesaccess to the spring arm 128 for pushing its end portion inwardly torelease it from the detent member 130 and moving it angularly to locateit on another detent 204. The bridge member 206 may be tapered to slopeinwardly towards detent member 130 to facilitate such deflection tochange the spring position.

If spring arm 128 is moved in a clockwise direction to a lower detent204, then a displacement angle, d, will decrease and the energy storedin spring 150 at the cocked position will be increased proportionally.Conversely, if spring arm 128 is moved in a counterclockwise directionto a higher detent 204, angle d increases and the energy stored inspring 126 at its cocked position will decrease proportionally. Thus, bymoving the fixed arm 128 to different locations along detent member 130,the energy stored in spring 150 at its cocked initial position may bevaried to adjust the drive force applied to disc 106.

As shown in diagrammatic form in FIG. 7, the lens focusing and shuttersystem are configured to be packaged as a modular subsystem 210 with themajor components thereof being mounted between the rear base block 49and the front cover plate 77. Such modular construction facilitatestesting and calibration before module 210 is mounted in the camerahousing.

The preferred method for deriving an indication of disc velocity is tomeasure the "ride-time" of the lens pawl tang 140 along the peripheraledge 176 between adjacent notches 142. That is, knowing the length ofthe edge 176 between notches and being able to measure the elapsed timefrom the initial contact with edge 176 by tang 40 to the time it iscammed into the approaching notch 142, one can calculate disc velocity.Since ride-time directly correlates to disc velocity, it can be used asa calibration reference for adjusting disc velocity.

In the illustrated preferred embodiment, ride-time of the lens pawl tang140 is measured electro-optically by observing the pivotal motion oflens pawl 20 utilizing the arcuate arm 160 thereon radiating outwardlyfrom arm 144 in the opposite direction from tang 140. Such pivotalmotion of arm 160 is employed to vary the amount of light transmittedthrough module 210 at a test station from test lamp 212 behind baseblock 49 to a photocell 214 on the forward side of cover plate 77 whichis ultimately displayed as an electronic trace on the face of cathoderay tube 216 of oscilloscope 218. The light transmission path from lamp212 to photocell 214 is transverse to the pivotal path of travel ofarcuate arm 160 on the lens pawl 20 and is defined by an opening 220 inbase block 49; and aligned opening 222 in the forward shutter blade 38and an aligned narrow slit 224 in cover plate 77 shown in dotted linesin FIGS. 2-4 and in solid lines in FIGS. 8 and 9.

In response to cycle initiation and rotation of the walking beam 62 in acounterclockwise direction to unlatch the shutter, lens pawl 20 pivotsin a clockwise direction to the position of FIG. 3 so that arm 160blocks a major portion of the light output slit 224 and the amount oflight transmitted to photocell 214 is at a minimum as indicated byportion A of the trace. In response to echo signal detection and thesolenoid de-energizaton command from the inverter gate network 174, thesolenoid 74 is deenergized and walking beam 62 rotates in a clockwisedirection allowing lens pawl 20 to pivot in a counterclockwise directionto engage tang 140 with the peripheral edge 176 between adjacent notches142 as shown in FIG. 8. In response to such motion, arcuate arm 160unblocks a larger portion of slit 224 thereby increasing the amount oftransmitted light toward a point indicated at B. During the ride-time,there is no pivotal motion of the lens pawl 20 because the peripheraledge portion 176 is of constant radius. Thus, the light output isconstant indicated by the straight horizontal portion C. When the tang140 is cammed into the approaching notch 142 as shown in FIG. 9, lenspawl 20 pivots abruptly in a counterclockwise direction thereby movingarcuate arm 60 downwardly to further uncover slit 222 and allowingmaximum transmission of light indicated by the steeply rising traceportion D. Thus, the length of the flat horizontal portion C provides anaccurate indication of ride-time, t, which is directly correlated todisc velocity.

In the calibration operation, the system is operated to measureride-time. If it is below a predetermined limit, indicating that thelens velocity is too fast, then the position of arm 128 is moved in acounterclockwise direction to a new detent 204 for the purpose ofreducing stored energy in spring 126 to reduce disc velocity.Conversely, if the ride-time is too long, indicating the the discvelocity is too low, then the position of arm 128 with respect to thedetent member 130 is adjusted to increase the energy stored in thespring 126 for increasing disc velocity.

It should be noted that the constant radius of the lens disc peripheraledge 176 serves two purposes. First, it stabilizes the position of lenspawl 20 during the ride-time in preparation for the camming of tang 140into notch 142. Also it thereby stabilizes arcuate arm 160 to facilitateproviding the smooth trace portion C during testing and calibration togive a more accurate measure of the ride-time, t.

Because certain changes may be made in the abovedescribed apparatus andmethod without departing from the scope of the invention hereininvolved, it is intended that all matter contained in the abovedescription or shown in the accompanying drawings shall be interpretedas illustrative and not in a limiting sense.

What is claimed is:
 1. A camera including an automatic lens focusingsystem for automatically focusing image forming light rays from aphotographic subject at a camera film plane, said cameracomprising:means for generating and transmitting a sonic ranging signaland for providing an indication upon detection of an echo signalreflected from a photographic subject at an elapsed time, subsequent totransmission of said ranging signal, indicative of camera-to-subjectdistance; a plurality of discrete lens elements each having a differentfocal length; a disc for holding said plurality of lens elements incircumferentially spaced apart relation to each other for rotation abouta center axis of said disc, rotation of said disc from an initialposition operating to sequentially move each of said lens elements intoposition to focus an image onto the film plane of a photographic subjectwithin a corresponding different camera-to-subject distance range, saiddisc including a peripheral section having a plurality of open outer endtang receiving notches therein extending generally inwardly from anouter edge portion of said peripheral section and being disposed incircumferentially spaced apart relation to each other, each of saidnotches being arranged in predetermined angular relation to acorresponding one of said lens elements and also being configured toinclude a leading side cam surface set at a cam angle with negative rakewith respect to a radial line passing through an outer tip of saidleading side cam surface, an oppositely spaced trailing side cam surfaceset at a cam angle with positive rake and extending further out in theradial direction than said leading side cam surface, a bottom surface,and a generally concave transition ramp surface extending between alower portion of said trailing side cam surface and said bottom surface,said outer edge portion being at a constant radial distance from saidaxis between notches except in the vicinity of the outer ends of saidtrailing side cam surfaces where it protrudes outwardly to accommodatethe extended portion of said trailing side cam surface; means foreffecting rotation of said disc away from said initial position so thateach lens element reaches said focusing position at a time subsequent tothe provision of a correlated echo signal indicating that the next lenselement approaching the focusing position is appropriate for thecorresponding camera-to-subject distance range; means for biasing saiddisc for rotation back toward said initial position; and meansresponsive to the provision of the correlated echo signal indication forstopping rotation of said disc to locate said corresponding lens elementat said focusing position, said stopping means including a pawl mountedfor pivotal motion toward and away from said peripheral section of saiddisc and having a tang configured to be releasably received in any oneof said disc notches to stop disc rotation and inhibit further rotationuntil it is removed from said notch, said tang including a leading sidesurface having a positive rake angle that is greater than the cam angleof said trailing side cam surface of said notch, a trailing side surfacehaving a negative rake angle that is greater than the cam angle of saidleading side cam surface and a concave bottom surface, having a radiusof curvature that is smaller than the radius of curvature of said discouter edge portion between notches, joining the lower ends of said tangleading and trailing side surfaces and cooperating therewith to defineleading and trailing end tang cam follower tips, the span between saidleading and trailing tips being narrower than the width of said notchopening, said pawl being locatable at an initial disengaged positionwherein said tang is spaced outwardly from said outer edge portion toallow rotation of said disc therepast and in response to said echosignal indication being actuable to pivot toward said disc so that atleast one of said leading and trailing end tips engages said outer edgeportion of said disc between adjacent notches ahead of an approachingone of said notches and rides therealong whereby said lens pawl ismaintained in a stabilized condition due to the constant radius of saidouter edge portion until said leading end tip of said tang is engaged bysaid extended portion of said trailing side cam surface of saidapproaching notch whereupon in response to further disc rotation towardsaid focusing position said leading end tip follows said trailing sidecam surface and then said concave ramp section to effect camming actionof said tang down into said notch to initiate stopping of disc rotation,said trailing end tip of said tang and said leading side cam surfacealso acting to cam said tang into said notch when engaged due tooscillating action of said disc responsive to abrupt disc decelerationwhen said tang enters said notch, said disc biasing means serving tobias said disc back toward said initial position to hold said leadingside cam surface of said notch in contact with said trailing end tip ofsaid tang located therein to accurately position said disc and therebylocate said corresponding lens element at said focusing position.
 2. Thecamera of claim 1 wherein the action of said tang leading end tipfollowing said concave ramp section of said notch aids in thedissipation of the inertial energy of said disc to facilitate stoppingdisc rotation with a minimum of oscillation.
 3. The camera of claim 1wherein the span between said leading and trailing end tang tips is onlyslightly narrower than said notch entry opening for the purpose ofextending the ride-time during which said trailing end time remains incontact with said outer edge portion after said leading end tip isprojecting into said notch entry opening thereby extending the timewherein said lens pawl is maintained in a stabilized condition.
 4. Thecamera of claim 1 wherein the rake angles of tang leading and trailingside surfaces are sufficiently larger than said corresponding cam anglesof said trailing and leading side cam surfaces to provide clearance andthereby restrict contact of said cam surfaces to said leading andtrailing end tips of said tang.
 5. The camera of claim 1 wherein saidcam angle of said trailing side cam surface is greater than said camangle of said leading side cam surface.